Squirrels, Ahoy! - Stuff You Should Know Recap

Podcast: Stuff You Should Know

Published: 2026-03-20

What Happened

Josh Clark developed an appreciation for squirrels through his dog, Momo, who enjoys feeding them. Squirrels are fascinating creatures with approximately 300 species found across every continent except Antarctica. They belong to the rodent order and the family Sciuridae, thriving in diverse environments such as mountains, forests, and even deserts.

Squirrels exhibit remarkable adaptability and diversity. The African pygmy squirrel, as small as a mouse, contrasts starkly with Bhutan's giant flying squirrel, which can exceed two feet in length excluding its tail. Squirrels are divided into three groups: ground squirrels, tree squirrels, and flying squirrels, each with unique adaptations. For instance, ground squirrels like prairie dogs live in large communal towns, while flying squirrels use a skin flap called the patagium to glide.

Ecologically, squirrels play a vital role in forest regeneration by planting new trees from forgotten nuts. Tree squirrels, like the eastern gray squirrel, are known for their agility and ability to descend trees headfirst by rotating their back legs. Ground squirrels, including chipmunks and marmots, have sophisticated communication systems and can identify relatives through scent.

Historically, squirrels migrated from North America to Eurasia 35-40 million years ago and later to Africa. An old saying suggested a squirrel could travel from Maine to Georgia without touching the ground, thanks to abundant chestnut trees. However, in contemporary times, eastern gray squirrels introduced to Australia died out, although some feral colonies persist.

Squirrels have evolved unique physical traits, such as continuously growing incisors, which can reach up to six inches annually. Their opportunistic diet includes nuts, fruits, insects, and occasionally eggs and birds. Interestingly, red squirrels in Maine have adapted to tap sugar maple trees for sap.

Squirrel populations have historically experienced migrations or 'stampedes' when densities were higher. In the late 19th century, squirrels were reintroduced to urban parks to enhance public mental health and teach children compassion. Their natural behavior of dashing in front of cars stems from an evolutionary predator evasion instinct.

Feeding squirrels can lead to increased populations and dependency on human-provided food. Peanuts, a common squirrel food, can carry harmful aflatoxin, making roasted peanuts a safer option. Black squirrels, a genetic variant of eastern gray squirrels, are more prevalent in certain areas like New York and Toronto.

Squirrels' impact on ecosystems and human environments extends beyond mere curiosity. Despite being viewed as vermin in the past, they have become integral to urban greenspaces, demonstrating nature's resilience and adaptability. The relationship between mass-producing trees and squirrel populations underscores their ecological importance.

Key Insights